Aircraft rotor providing for tilting of axis and blade pitch regulation



June 29, 1948. p, H STANLEY 2,444,070

AIRCRAFT ROTORS PROVIDING FOR TILTINC- `O AXIS AND BLADE FITCH REGULATIONS F11ed` May 14, 1942 2 Sheets-Sheet l ,l iwi,

QQWMTORN Ys June 29, 1948. P. H. STANLEY AIRCRAFT Ro TORS PROVIDING FOR TILTING vOF AXIS AND BLADE FITCH REGULATIONS 2 Sheets-Sheet 2 Filed May 14, 1942 lryA/'TOR BY M/ @jy/MM XTTORNEYJ Patented June 29,?1948 AIRCRAFT ROTOR PROVIDING FOR TIL'IING OF AXIs AND BLADE PI'rcH REGULATION `Paul H. `Stanley,`Huntingdon Valley, Pa., assignor to Autogiro Companyof America, Philadelphia, Pa.,a corporation of Delaware I Application May 14, 1942, serial No.V 442,911

Aircraft sustaining rotors commonlyI incori porate a hub and a pluralitypf blades connected with the hub by means of oneor more` pivots including, at least, aiiapping pivot. ,During operation of such aircraft, the rotor moves ,through the air more or less edgewise, the` translational flight movement being set up eitherby the` employment of aseparate propulsive airscrew (as is customary in autorotative winged aircraft) or by tilting the axis of the rotor (as is frequently proposed for helicopter operation) l event, the blades experience a wide variation in the direction and Velocity of local airflow over the surfacesthereof, the blade advancing in the direction of translational iiight being subject to airflow of muchhigher velocity than `the blade which `is retreating with respect tothe Hight' part, for the iiuctuations in `eifective,aerodynamic 'im angle of attack introduced during` translational 30 night. l y 1 l ,A

`Additional-Init is an important object of this invention to provide means automatically chang- In either ,l

`vantagesare attained will vappear more clearly ing blade pitch angle in ia sense to shed, the ...al

effect of air bumps `or other disturbances, many of which also tend to setup wide variations in eiective aerodynamic angle of attack.

Undesirably extensive variations iniangle of attack occur at times during maneuvering of the aircraft, and especially during sharp maneuvers. Moreover, these conditions are particularly noticeable in helicopter type aircraft, wherein the range of iiight speeds may vary all the way from true hovering `torelatively high speed translational flight, and wherein the rotor mayat times be horizontal (as in hovering) or inclined down- Wardly and forwardly (as in translational iiight)'.

`It has been found,` in fact, that the *eiect'of air disturbances or sharp maneuvering in an airbeen increasedmomentarily beyond the stallingV point.

The arrangement of the invention automatically introduces compensating movements ofthe blades in the pitchchange sense, whereby to reduce or substantially neutralize fluctuations in aerodynamic angle of attack even during sharp maneuvering of a helicopter type machine.

It is a further object of the invention to provide a manually operable mechanism for introducing periodic differential pitch change of the blades, the action of which and of said automatic pitch control means is superimposed one upon the other, thereby providing the advantages of both. Still further, the invention has in view the provision ofmeans for simultaneously `varying the pitch of all blades in the same sense, this simultaneous pitch control also being independent in its action, so` thatpitch changes of all three types may simultaneously occur. mIn accordance with anotheraspect of the invention, novel structural features are employed inthe blade mounting and also in the hub mounting, as will further appear.

How the foregoing and other objects and adfrom the following description, referring to the accompanying drawings, in Which- Figure 1 is a vertical sectional View of a rotor hub and mount, the View being taken substantially as indicated by the section line I-I on Figure 2; andV Figure 2 is a plan view, partly in horizontal section and partly in elevation, illustrating portions of the hub shown inFigure 1.

The rotor hub may be mounted on flxed, struc- ,ture 3. Asupport 4 is carried on this structure,

and within the support a pair of bearings 5-5 cooperates with the rotative 4hub spindle 6. A

.non-rotative sleeve 1 'is secured to and extends upwardly from the support 4, a bearing 8 being ,operatively interposed between the upper end pf thissleeve and the rotative spindle 6. e

Y `At a point spaced appreciably above the upper end of the sleeve 1, the spindle 6 is provided with ,a universal joint 9, this joint vserving to carry the spindle extension I0 to which the bell shaped rotative `hub `Il is connected. VThe joint may desirably be of the constant velocity type so as to enhance smoothness of torque transmission to the hub regardless of the tilted position of the hub on the universal joint.

The spindle 6, and thus the hub, may be driven 4by, means of a gear I2 meshing with a pinion I3 which, in turn, is adapted to be driven from the power shaft I4, ythe latter being connected with any suitable prime mover in the body of the machine. f the aircraft is of the ipurely autorotative winged type, shaft I4 would ordinarily be coupled with the engine employed to drive the usual propulsive airscrew. In that type of helicopter in which no propulsive airscrewis employe d,theengine would ordinarily be provided chiefly, if. not solely, for rotor driving purposes.

In any event, it is contemplated that suitable overrunning and manually controllable clutches should be incorporated in the drive transmission, so that the rotor may rotate freely, at least :for the purpose of descent without mower, with theblades` 4 mechanism for controlling swinging'` movement of the blades are claimed in my divisional application No. 18,383 filed April 1, 1948.

For the purpose of controlling the pitch angle thereof, each blade is provided with a control arm 33 which is rigidly connected with the sleeve jganddmay, therefore, Mbe used ,tocause the blade :to move' about itsownlohgitudinaliaxis (the axis defined by bearings 21). Asseen 'in Figure 2, the

'with reference to the direction of rotation of the 1 rotor (indicated :by ,arrow R), the extension of clutch including toothed parts -I5 and yI6, thelatrotor 'shall incorporate Vthree `blades, and Ait may be 'mentioned that, in accordance with'the invention, the rotor preferably inconporates at least threeblades this .being oiimportance for reasons which will further appear. .The inner end of one suchblade appears at ,19, this 'blade having a root end mounting member the inner end of which is '22. Block 2l is 'forkedto receive'link '23, the link `and block being interconnected' by a appingpivot 24,' providing freedom for blade swinging move- 'ment in a direction generally transverse the mean p rotative path of travel of the blades.

Link 23 projects into a sleeve 25,.the sleeve and linkbeing interconnected'by a .drag pivot 26, `providing freedom yfor lag-lead movement of vrthe blade.

bearings 21,'the' axisofwhich ispreferably vvcoincidentwitht'he'longitudinal axis df the blade, thereyby providing forpitch change movement of .the blade.

35 Vthreaded into a blockfvl, being secured by a nut .4 5 jSle'eve 2 5 isjournaled'inthefhub' I I by means of VThe 'lag-lead movement of the rseveral blades"v 'maybe controlled' by means of a damper device arranged within and concentrically of the hub, each 'blade having lan inwardly projectingarm 28 cooperating with aring .segment 29 (seeFigure 2).

The ends of the several segments 29 are spaced` "from each other, and above Vand'belo'vv the segments,-friction discs 30 are backedby rubber rings 3|, so as to restrain movement ofthe segment about the axis of `the hub. Thereby, Amovenients `of the blades in the lag-lead sense restrained. I

*Since the hubis free to 'float 'about'the 'center point of universal joint @fthe damper 'device Ade'- scribed just abovejis also mounted for similar arei damped or floating movement, a'spherical seat 32 being provided for this purpose; Preferably'the damper deviceis free to rotate with respect'to Yhub spindle lifthe effect of which is to permit unrestrained simultaneous llag-lead movementof vall 'of the blades in the same sense. Relativelag-leadjmovement vof the blades (for instance, one :iforwardly and another rearwardly) is, *howeven'restraine'd by the actionof` the damper device.

The dainpe'rdevice and other features Aof'tli'e the` arm .preferably being to a point approximatelyrl90 .in advance of the blade. A vertical link 34 '(see Figure 1) interconnects control arm 133 and .one `end of a lever 35, ball and socket joints 36 and 31 being provided at the upper and lower Jendsof link 34. Lever is pivoted intermediate 4.its ends, as indicated at 38, the other end of the lever being connected by means of a link 39 with the hub ymember I I, ball and socket vjoints 4U and 4I again 'being `provided in this llink connection.

Lever 35 is mounted on abracket42 projecting from rotative Yring 43, it being understood vthat the' linkage parts above -described (33 to 42 inclusive) yareduplicated for'eachblade. Ring 43, in turn, :is mounted Vonswash member -44 'by means of a bearing 45, the swash lmember beingitiltable vin all directions on the lball 46.

i lRing 43 `is constrained to rotate with the rotor by a scissors linkage including Ylink parts 41 and 48. The upper member 41 of the scissors linkage is pivoted toa bracket -49 carriedby and `rotating lwith the spindle t.' The llower -end of link 48 is connected with a bracket 50 carried lby ring '543. 'The joints 5I, '52 and 53 .in this linkage are vsuch-as to constrain the ring v43 to rotatev with the rotor and yet to vpermit :freedom for `tilting -movement of ring :43 about the center yof Iball 46, .and lalso to rpermit Ivertical movement of ring 43 by means of certain control connections referred to -herebe1ow. --For this purzpose, a single pivot pin Vmay Kbe lused yfor joint -5I and also for joint-152, although joint 5,3 preferably comprises a `universal-or Aball joint, the -center of which -is `desirably located in the same :plane as `the center `of ball-4B -about which -ring 43 Iis tiltable. f

Tilting :movement of swash i member '44 may be beilectedthroughthe depending control tube 54, which is slotted as at in order to permit 'free frelative rvertica'l movement of Atube 54 and the cooperating-actuating Apart 56, Ywhich vlatter is providedwithaball151 interiorly of the tube. The operating 1partlf56 projects 'from the upper end of lcontrol arm 58, constituting an :extension of the manually .operable lacontrol lmember 59 which lis carried on afiixed-bracket' by meansofa-uni- -versal joint fel. L'The manual -control 59, may, therefore,:.be swungfinanyldirection, and'through the arm 15B and 4parts 54 nto l1551, these swinging movements may :be employed :to :tilt 'the swash .memberf44, likewise inany direction.

lThe :ball 46, which constitutes lthe 4seat lfor .swash member 44, lhas a .downwardly extending sleeve 3,2.car1'ying .an apertured lug 63 by which the .ball 4 5 *and .thus the :swash member, .ring .43 and.associatedparts.maybe moved vertically. A control for this `purpose includes .a lever 64 pivotedat `to a ixed bracket 66,.the.free:end of this lever cooperating .witha manual ,.control, suchas .the'push-pull tube 61.

In"consideringthe operation of the .foregoing mechanism itis first to'be observedthat the hub superimposed upon each other.

maneuvering.

A90" beyond the point of th-e disturbance.

AI:I,:Iar`1d` thus the entire rotor, is freeto tilt `in any direction about the center` point of the universal joint 9...

The hub and the rotor blades are, `therefore,.free floating and may take up dif- .ferentuplanes of rotation, depending upon the `forces acting upon the blades. Normally, the

blades assume an average position dening a very ilat cone, the `.dapping pivots 24 providing the .necessary freedom for the blades to move to this 'matic, although it may here be noted that the action of each pitch `variation is independent of the other, vin the sense that they may take place independently at different times, or at the same time, in which latter case the several eiects are In analyzing the `three types of pitch change, reference is rst made to the automatic pitch variation. Assume that the control ring 43 is maintained in a horizontal plane, as shown in Figure 1. In thiscondition, tilting of the hub ll about the universal 9 will introduce changes of blade -pitch angle. For instance, if the hub tilts :downwardly at a point 90 in advance of blade I9, as shown in Figure 2, the link 39, whichis `attached to thehub by joint 40, `will similarly be `caused tofmove downwardly, thereby rocking arm 35` and causing link 34 to move upwardly, this latter link being connected with` arm 33 by joint 36. It will `be seen that tilting movement of the hub in thesense just mentioned causes `an increase of the pitch angle of blade id (Figure 2).

Thus, tilting movement of the hub in one plane causes a change in the eiective aerodynamic angle of attack of the blades as they pass through an azimuth generally at right angles to the plane of hub tilting.

` Attention is now directed to the fact that, as vshown in Figure 1, pivot 38 for lever 35 is located closer to the outer end'of the leverthan to the inner end thereof, in view of which (in the above example) a given angular tilting movement of the hub will produce a 'larger angular movement (pitch increase) of the blade. This ratio may not always be required but is of advantage under at least some, conditions, or in certain machines, in l correcting for `the effect of disturbances which may be brought about, for example, during sharp In further explanation, it is pointed out that thev effect of a disturbance at one side of the rotor `is to set upa force tending to tilt the ro- ,tor hub in a plane at right angles to the point at which the disturbance occurs. Thus, for example, if a disturbance occurs at the left-hand side of Figure 2, the disturbance being in a sense causing decrease of effective aerodynamic angle of Aattack of blade I9, the blade will tend to ride to a lower position, reaching the lowest point Such a disturbance, therefore, causes the hub Il to tilt downwardly approximately 90 beyond the position of blade I9. This tilting movement of the hub will influence the pitch of the next following blade so that when it reaches the posiktion at the left of Figure 2, its pitch angle will be increased, thereby compensating for the loss lmechanismas illustrated` by virtue of location of pivot 38 closer to the outer end of lever 35 than to the inner end thereof. It is also contemplated that pivot 38 may be disposed midway between the two ends of lever 35, or may even be disposed closer to theinner end of lever 35 than to the outer end thereof.

It will belunderstood, of course, that the action of the pitch control linkage as just described, takes place in opposite senses at diametrically opposite sides of the rotor, this being desirable in order. to provide similar compensating conditions throughout the entire circle of rotation. It may also be mentioned that the compensation referred to takes place regardless of the point where the disturbance occurs and, therefore, regardless of the direction of tilting of the hub.

Turning now to the manual controls, it is first mentioned that the control 6l, by means Yof which the swash member 44 may be -moved upwardly or downwardly, provides for simultaneous increase and'decrease of the mean pitch of all blades of thev rotor. This takes place by virtue of raising and `lowering the pivotal mounting 38 for the several levers 35. When these pivot points (38) are .raised the pitch of all blades is increased, and when lowered the pitch is decreased. Thus, the control 61 may be" used to alter the operating conditions of the machine. For example, assuming a helicopter normally having its rotor power driven with the blade angle relatively high, if it is desired to descend without power, the blade angle may be reduced to an appropriate autorotative value.

The control 59, by means. of which the swash member may be tilted, is provided primarily for maneuvering purposes. This control operates to raise the pivot point 38 at one side of the rotor and to lower said point at the opposite side, depending upon vthe direction in which the control 59 is displaced. The eifect of differentially raising and lowering opposite Ipivot points 38 is to introduce periodic differential pitch change of the blades, thereby shifting the lift line of the rotor which in turn, introduces controlling moments in the lateraland longitudinal directions. The control hook-up is preferably such that instinctive control is provided of the general character more fully disclosed in copending application of Juan de la Cierva, Serial N o. 698,372, filed November 16, 1933, which issued as Patent No. 2,380,582 (corresponding to British Patent No. 410,532). With such a hook-up, when the control stick (or equivalent manual control organ) is moved fiorwardly, the pitch of the blades at the advancing side of the rotor is decreased and the pitch of the blades at the retreating side of the rotor is inn creased. The opposite effect takes place upon movement of the contr-o1 stick rearwardly. A

fsimilar action is contemplated for lateral control,

.by movement of the stick to `the ,right orto the lef; Y

Both oi the manual vcontrols referred to just above operate substantially independently of the .antomatic control although, as above pointed out.. i all `three controls may operate simultaneously, in

which eventtheir action is superimposed.

I claim: ,Y

1. For an air-craft, a bladed sustaining rotor incorporating a plurality of blades and a hub, each blade being pivotally connected with `thefhub on an laxis oiset from the rotational axis thereof and providing for swinging movement of the blade in afdirection generallytransverse the mean rotative path of travel of the iblades, means :mounting the hub for rfree, .tilting movement in all directions, whereby said hub may -iioat to `and rotate -in different `planes under the influence of blade swinging movements, means providing for pitch change of each blade, and pitch control means for the blades including, for each blade, linkage interconnecting the blade and the hub and providing for increase of blade pitch with respect to the hub upon tilting movement of the hub in a plane angularly offset from said. blade.

2. A construction in accordance with claim 1 in which the pitch control means provides for increase of blade pitch with respect to the hub uponr downward tilting movement of the hub-at a point angularly oiset from the blade in the l-eading direction, with referencetothe direction of rotation of the rotor.

3. A construction in accordance withclaim 1 in which the .pitch control means provides for increase of blade pitch with respect to the hub upon downward tilting movement of thehub ata point angularly offset approximately at right .angles from the blade in the leading direction, withref- ,ing movementameans providing for pitch change of Ieach blade, and mechanism for controlling the pitch of -the several blades including, for each blade, a control arm projecting gen'erallyicircum- ,ierentially of the hub to a point angularlyoiset ,from the-blade,and control linkage interconnecting Isaid arm and the hub at a point in the region of the point first mentioned and providing for variation of pitch of said .bladeupon tilting of the .hub in a vertical plane containing the rotor axis and the said point to which the control linkage is ,connected Iwith the hub.

5. A construction in accordance With claim 4 in which said control linkage provides for increase of vblade vpitch upon downward tilting movement `of 'the hub at that side at which the control linkage is connected therewith.

6. For an aircraft, a bl'aded sustaining rotor comprising a hub and a plurality of blades, each yblade being pivotally connected with the hub on an .axis offset from .the rotational axis of the hub `and providing freedom for blade swinging move- -ment in a direction generally transversethe mean rotative path of travel of the blades, means mounting said hub for lfree tilting imovement in ,all directions, whereby said hub may freely float sel( to different positions iunder .the influence of .blade vswinging Amovements.means providing forpitch variationof each blade -with respecttothe oating hub,y and-,mechanism for contnolling lthe pitch position of the ,blades including, for each blade, .a lever pivotally mounted intermediate its ends, linkage connecting one end .ofvsaid lever andthe blade to `provide for pitch change movement of the blade upon pivotal movement .of the lever, and Alinkage interconnecting the -other end gof said lever andthe noating hub, .thepoint .of ,connection of said :last ymentioned linkage with the floating hub being angularlyoisetfrom the zblade, the said pitch control mechanism being `arranged .to provide for increase of blade pitch upon downward tilting movement ,of the `hub at ,that side at ywhich said linkage lis Aconnected therewith.

7. A construction in accordance with claim r6 and further incorporating a controllably tiltable swash member rotatable with the rotor, ythe said lever of the pitch control mechanism being pivotally mounted on said swash member, and controllable means for varying the plane of rotation of said swash member.

8. A construction in'accordance with claim and further including controllable means for raising and lowering the pivotal mountings for the several levers of the pitch control mechanism simultaneously in the same sense.

9. A construction in accordance with claim 6 and further including means for raising and lowering the pivotal mountings for the several levers of said pitch control mechanism differentially and periodically during rotation of the rotor.

10. A construction in accordance with claim 6 and further incorpo-rating a controllably tiltable swash member rotatable With the-rotor, the said lever of the pitch control mechanism being pivotally mounted on said swash member, and con- -trollable means for `varying the plane of rotation of said swash member, and further including controllable means for raising and lowering said swash member, whereby to simultaneously vary the pitch of all bladesin the same sense.

V11 For an aircraft, a sustaining rotor including a hub member mounted for rotation and -for tilting movement in all directions, a -plurality of blades, each pivotally connected with the hub on an axis offset from the rotational axis of the hub and providing freedom for swinging movement of the Ablade in a direction generally transverse the mean rotative path of travel of the blades, means providing for pitch change of the blades, and mechanism for controlling the pitch angle of the blades including, for each blade, a control arm connected With the blade and extended circumferentially of the hub to a point appreciably offset from that blade, a lever pivotally mounted intermediate its ends, linkage interconnecting one end of said lever and said control arm, and linkage interconnecting the other end of said lever and the hub at fa point in the region of the point first mentioned.

12. For an aircraft, a bladed sustaining lrotor comprising a plurality ofr blades having a common central tilting member on which they are pivotally `mounted and which in turn is mounted for rotation in addition to tilting, and mechanism for effecting cyclic pitch variation of the blades upon tilt of said member, including pitchcontrolling linkages for the several blades operatively coup-led respectively to said member at points substantially angularly removed from the respective blades which they control and coupled .to the blades to eect a .maximum of such .cyclic pitch variation of each blade with reference to the aircraft when the blade reaches a position in its rotation correspondingly substantially angularly removed from the plane of tilt of sai-d member.

13. For an aircraft, a bladed sustaining rotor comprising a plurality of blades having a common central tilting member on which they are pivotally mounted and which in turn is mounted for rotation in addition to tilting, mechanism for effecting cyclic pitch variation of the blades upon tilt of said member, including pitch-controlling linkages for the several blades operatively coupled respectively to said member at points substantially angularly removed from the respective blades which they control and coupled to the bla-des to effect a maximum of such cyclic pitch variation of each blade With reference tothe aircraft when the blade Ireaches a position in its rotation correspondingly substantially angularly removed from the plane of tilt of said member, and means for eecting cyclic blade pitch variation at will.

14. For an aircraft, a bladed sustaining rotor comprising a plurality of blades having a common central tilting member on which they are pivotally mounted and which in turn is mounted for rotation in addition to tilting, mechanism for effecting cyclic pitch variation of the blades upon tilt of said member, including pitch-controlling linkages for the several blades operatively coupled respectively to said member at points substantially angularly removed from the respective blades which they control and coupled to the blades to effect a maximum of such cyclic pitch variation of each blade with reference to the aircraft when the blade reaches a position in its rotation correspondingly substantially angularly removed from the plane -of tilt of said member, and means operative by the pilot for effecting cyclic and collective blade pitch variation.

PAUL I-I. STANLEY.

REFERENCES CITED The following references are of record in the file of this patent:

'UNITED STATES PATENTS Number Name Date 1,992,015 Rutherford Feb. 19, 1935 2,030,578 Flettner Feb. 11, 1936 2,150,129 Pecker Mar. 7, 1939 2,153,610 Campbell Apr, 11, 1939 

